Several different types of methods and arrangements of the aforesaid nature are known to the art.
A gas sensor that utilises an infrared (IR) spectrometer technique in accordance with U.S. Patent Publication U.S. Pat. No. 5,550,375 can be mentioned as a first example of the technical background of the invention and the technical field to which the invention belongs.
This prior publication illustrates and describes an arrangement which, in principle, utilises the possibility of detecting a gas and/or the concentration of the gas selectively with the aid of an IR spectrometer, by establishing the specific absorption wavelengths of the gas and evaluating the intensity of the gas in its gas-significant wavelengths within the infrared spectral region.
The gas sensor illustrated in said prior publication is particularly adapted for the continuous control of a gas flow or a gas-filled cavity, where the sensor or cell body is comprised of one single part and is produced as a body of microstructure.
The cavity in the gas cell includes a wall-related mirror grating placed between the input and output openings for beams of infrared light.
According to the embodiment, illustrated in FIG. 1B, a light bundle having divergent light rays is emitted from the light source (7) through a gap or opening (3) onto a first concave mirror surface (5) from which it is reflected obliquely onto a planar grid or grating surface (2) and there reflected or diffracted obliquely as a light wave onto an adjacent concave second mirror surface (8) so as to be able to pass through the output opening (4) as a convergent light bundle.
It is shown that the body or a gas-cell base plate (1) can be produced via X-ray, lithographic etching, electroplating and moulding processes, via the LIGA process.
The gas sensor shown and described in the International Patent Publication WO-A1-98/09152 is another example of the technical background and the technical field applicable to the present invention.
This latter prior publication illustrates a gas sensor (A) adapted for evaluating the composition of a gas sample enclosed in a cavity (2) or in a gas cell.
The gas cell has been shown in the form of a block, where cavity walls and cavity wall sections are said to have a very high light reflecting ability and are designated mirror surfaces (11A, 12A).
The cavity (2) includes an opening (2a) for incoming light rays which shall be reflected within the cavity a predetermined number of times such as to define a requisite measuring path or extremity before exiting through an output opening (6).
More particularly, the prior publication teaches the use of three mutually opposite and concave light-reflecting wall portions (11, 12, 13) in the gas cell.
A first wall portion (11) has the form of a semi-ellipse or ellipsoid.
A second (12) and a third (13) of said wall portions have a similar form, conforming to a part of a semi-ellipse or ellipsoid.